The purpose of the present study is the development of a co-robotic active catheter system for performing atrial fibrillation ablation under real-time intra-operative magnetic resonance imaging (MRI) guidance. The proposed research will synergistically integrate high-speed MRI technologies with robotic motion planning and control techniques to develop a novel co-robotic system. Specifically, the research will focus on i) development of new models, algorithms, and open source software for robotic motion planning and control of active catheter systems, ii) development of algorithms for achieving real-time intra-operative MRI acquisition and image reconstruction, and, iii) hardware realization and experimental validation of the developed technologies in benchtop and in vivo studies in collaboration with clinical partners. The intellectual merit of the proposed research comes from the scientific contributions to the individual fields of robotics and medical imaging as well a novl and synergistic integration of the two technologies. The research will advance the state-of-the-art in robotics, by pursuing robotic control, planning, and sensing algorithms that can not only handle the complicated state-space and system dynamics, but also the uncertainty about the state-space, often present in dynamic and deformable environments. The rapid MRI imaging methods developed here will allow real-time data collection and image reconstruction at a previously unattainable rate. They will enable rapid anatomical imaging of the heart, but also be relevant to other dynamic MRI applications besides cardiac imaging. This will be the first demonstration of a real-time guided MRI procedure where the anatomy and catheter can be completely visualized in real-time with clinical quality images. With this technology, further improvements in both interventional MRI as well as structural and functional imaging will be possible.